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为平均值滤波器生成代码

此示例说明使用 codegen 命令从 MATLAB® 函数生成 C 代码的建议工作流。步骤如下:

1.向 MATLAB 函数添加 %#codegen 指令,以指示它用于代码生成。此指令还使 MATLAB 代码分析器能够识别特定于 MATLAB 的代码生成警告和错误。

2.生成 MEX 函数以检查 MATLAB 代码是否适用于代码生成。如果发生错误,您应在生成 C 代码之前将其修复。

3.在 MATLAB 中测试 MEX 函数,以确保它在功能上等同于原始 MATLAB 代码,并且不会出现任何运行时错误。

4.生成 C 代码。

5.检查 C 代码。

前提条件

此示例没有任何前提条件。

关于 averaging_filter 函数

averaging_filter.m 函数充当输入信号上的平均值滤波器;它采用值的输入向量并计算向量中每个值的平均值。输出向量的大小和形状与输入向量相同。

type averaging_filter
% y = averaging_filter(x)
% Take an input vector signal 'x' and produce an output vector signal 'y' with
% same type and shape as 'x' but filtered.
function y = averaging_filter(x) %#codegen
% Use a persistent variable 'buffer' that represents a sliding window of
% 16 samples at a time.
persistent buffer;
if isempty(buffer)
    buffer = zeros(16,1);
end
y = zeros(size(x), class(x));
for i = 1:numel(x)
    % Scroll the buffer
    buffer(2:end) = buffer(1:end-1);
    % Add a new sample value to the buffer
    buffer(1) = x(i);
    % Compute the current average value of the window and
    % write result
    y(i) = sum(buffer)/numel(buffer);
end

%#codegen 编译指令指示 MATLAB 代码用于代码生成。

创建一些样本数据

生成噪声正弦波并绘制结果。

v = 0:0.00614:2*pi;
x = sin(v) + 0.3*rand(1,numel(v));
plot(x, 'red');

Figure contains an axes object. The axes object contains an object of type line.

生成 MEX 函数用于测试

使用 codegen 命令生成 MEX 函数。codegen 命令会检查 MATLAB 函数是否适用于代码生成,并生成 MEX 函数,您可以在生成 C 代码之前在 MATLAB 中测试该函数。

codegen averaging_filter -args {x}
Code generation successful.

由于 C 使用静态类型,codegen 必须在编译时确定 MATLAB 文件中所有变量的属性。在这里,-args 命令行选项会提供一个示例输入,以便 codegen 基于输入类型推断新类型。使用上述步骤中创建的样本信号作为示例输入可确保 MEX 函数使用相同的输入。

默认情况下,codegen 在当前文件夹中生成名为 averaging_filter_mex 的 MEX 函数。这允许您测试 MATLAB 代码和 MEX 函数,并将结果进行比较。

在 MATLAB 中测试 MEX 函数

在 MATLAB 中运行 MEX 函数

y = averaging_filter_mex(x);
% Plot the result when the MEX function is applied to the noisy sine wave.
% The 'hold on' command ensures that the plot uses the same figure window as
% the previous plot command.
hold on;
plot(y, 'blue');

Figure contains an axes object. The axes object contains 2 objects of type line.

生成 C 代码

codegen -config coder.config('lib') averaging_filter -args {x}
Code generation successful.

检查生成的代码

-config coder.config('lib') 选项的 codegen 命令可生成打包为独立 C 库的 C 代码。生成的 C 代码位于 codegen/lib/averaging_filter/ 文件夹中。这些文件是:

dir codegen/lib/averaging_filter/
.                              ..                             _clang-format                  averaging_filter.a             averaging_filter.c             averaging_filter.h             averaging_filter.o             averaging_filter_data.c        averaging_filter_data.h        averaging_filter_data.o        averaging_filter_initialize.c  averaging_filter_initialize.h  averaging_filter_initialize.o  averaging_filter_rtw.mk        averaging_filter_terminate.c   averaging_filter_terminate.h   averaging_filter_terminate.o   averaging_filter_types.h       buildInfo.mat                  codeInfo.mat                   codedescriptor.dmr             compileInfo.mat                examples                       interface                      rtw_proj.tmw                   rtwtypes.h                     

检查 averaging_filter.c 函数的 C 代码

type codegen/lib/averaging_filter/averaging_filter.c
/*
 * File: averaging_filter.c
 *
 * MATLAB Coder version            : 23.2
 * C/C++ source code generated on  : 03-Aug-2023 18:51:54
 */

/* Include Files */
#include "averaging_filter.h"
#include "averaging_filter_data.h"
#include "averaging_filter_initialize.h"
#include <string.h>

/* Variable Definitions */
static double buffer[16];

/* Function Definitions */
/*
 * Use a persistent variable 'buffer' that represents a sliding window of
 *  16 samples at a time.
 *
 * Arguments    : const double x[1024]
 *                double y[1024]
 * Return Type  : void
 */
void averaging_filter(const double x[1024], double y[1024])
{
  double dv[15];
  int i;
  int k;
  if (!isInitialized_averaging_filter) {
    averaging_filter_initialize();
  }
  /*  y = averaging_filter(x) */
  /*  Take an input vector signal 'x' and produce an output vector signal 'y'
   * with */
  /*  same type and shape as 'x' but filtered. */
  for (i = 0; i < 1024; i++) {
    double b_y;
    /*  Scroll the buffer */
    memcpy(&dv[0], &buffer[0], 15U * sizeof(double));
    /*  Add a new sample value to the buffer */
    b_y = x[i];
    buffer[0] = b_y;
    /*  Compute the current average value of the window and */
    /*  write result */
    for (k = 0; k < 15; k++) {
      double d;
      d = dv[k];
      buffer[k + 1] = d;
      b_y += d;
    }
    y[i] = b_y / 16.0;
  }
}

/*
 * Use a persistent variable 'buffer' that represents a sliding window of
 *  16 samples at a time.
 *
 * Arguments    : void
 * Return Type  : void
 */
void averaging_filter_init(void)
{
  memset(&buffer[0], 0, 16U * sizeof(double));
}

/*
 * File trailer for averaging_filter.c
 *
 * [EOF]
 */